1. Field of the Invention
This invention relates to a combination smoke machine and nitrogen generator having particular application for providing a mixture of “smoke” and nitrogen gas to a closed fluid system (e.g., the evaporative or air brake system of a motor vehicle) that is undergoing testing for leaks. The combination is advantageously compact, lightweight, easy to transport in the hand of a user and capable of relatively long operation with little downtime or maintenance required.
2. Background Art
Smoke generating apparatus are known for generating a visible gas or vapor that is mixed with air supplied thereto under pressure so that the mixture can be delivered to a fluid system undergoing testing for leaks. While such apparatus are commonly described as smoke machines, the “smoke” may be a non-toxic aerosol mist produced by evaporation and condensation at controlled temperatures rather than actual smoke which is a product of partial combustion and tends to contain toxic combustion byproducts. Hence, in the preferred embodiment to be described below, “smoke” refers to either a (e.g., petroleum-based) solution that is heated and vaporized or to a visible aerosol mist, spray, gas, vapor or combination thereof that is heated or not. Some smoke generating apparatus have been used to detect leaks in the evaporative system of a motor vehicle. By observing any visible “smoke” which exits a small and often visually imperceptible hole in the system under test, an indication is provided to the observer of the presence and location of the leak so that a repair might be made.
Because of the concerns for the environment, it has become even more important to be able to test the integrity of the evaporative system of a motor vehicle so as to determine the presence and the location of a leak in need of repair. To accomplish the foregoing, smoke has been mixed with and carried by nitrogen gas, rather than air, from a smoke generator to the system under test. Nitrogen gas is an ideal carrier for the smoke because of its non-flammable and inert characteristics. That is, the smoke and nitrogen gas are relatively safe for testing systems which lie in a generally volatile environment and are surrounded by potentially explosive hydrocarbon vapors. Therefore, mixing smoke and nitrogen gas provides a safe and efficient means for locating a leak in the evaporative system of a motor vehicle. Moreover, providing a supply of smoke to the system undergoing testing by means of a nitrogen gas carrier, rather than air, enables a variety of high pressure systems, such as an air brake system and the like, to be tested at high operating temperatures, but without the inherent risk of an explosion. Reference may be made to U.S. Pat. No. 6,526,808 issued Mar. 4, 2003 to the assignee of this application for an example of a smoke-generating machine which employs nitrogen gas to carry smoke to a system being tested for leaks.
Nitrogen gas to be used alongside a smoke machine is often stored in and dispensed from relatively long, heavy and bulky cylinders that are inconvenient to lift and transport. Consequently, the nitrogen cylinders are commonly moved from place-to-place on a correspondingly large cart or inside a large cabinet. What is more, such nitrogen gas cylinders must be refilled from time-to-time which introduces added cost and delay to the leak testing process. Because of its size, it may be impractical to incorporate a traditional nitrogen gas cylinder with a smoke machine to achieve a compact, fully-integrated assembly that can be lifted and transported in the hand of a user.